Five university buildings were evacuated during a chemical alert yesterday.

Around a thousand students fled the West Cambridge Site after a leak of ethylene gas was discovered at the Cavendish Laboratory buildings at 1.30pm. Students also had to leave the CAPE Building, the Nano Science Building and two others.

The leak was caused by a fault on a 50-litre cylinder containing the gas, and fire crews from Cambridge and St Neots set up a 200m exclusion zone around the area before entering the buildings to monitor the gas levels inside.

A hazardous material team also attended.

Speaking at the scene, Martin Brown, station manager of Cambridge Fire and Rescue, said: “Ethylene is highly flammable and explosive and the on-site teams did everything right in evacuating.”

The buildings reopened at 3.10pm, allowing the students to continue with their work.

Joe Munns, who is doing a physics MA, had to leave the Mott Building in the middle of a practical experiment using hot plates.

He said: “I was working on an experiment and had to stop and quickly tidy everything up.

“I went and grabbed a coffee and I’m now going to see if I can get back to work.”

Eugenia Cammarota, a physics PhD student, was in the main Cavendish building when she had to leave a conference.

The 28-year-old said: “I had the same idea as most other people and went for a coffee.

“It wasn’t too disruptive.”

No-one was injured during the leak and evacuation and the fire service praised the actions of the public at the scene.

A Cambridgeshire Fire and Rescue Service spokesman said: “The fire service would like to say a big thank you to everyone in the area and the building for evacuating properly and thanks to all that it went to plan and went very well.”